In the modern era of rapidly developing technology, it is in need of an effective antenna that is small enough to be embedded in modern handheld or portable electronic device for wireless communication. For instance, there are antennas designed for cellular phones, notebook computers, or external wireless transmission devices, such as access points (APs) and card buses. Generally, there are two types of antennas, i.e. the planar inverse-F antenna (PIFA) and monopole antenna, that are already been used in the modern handheld electronic devices since they are advantageous in their simplicity in structure and good transmission performance. Taking the PIFA from the aforesaid conventional antennas for instance, for enabling signal from an electronic device to be transmitted out through a PIFA that is electronically connected to the electronic device through a coaxial cable, the electric connection between the two is generally achieved by connecting the inner conductive layer and the outer conductive layer respectively to the signal feed point and the ground point of the PIFA. Moreover, although the monopole antenna is a well-developed and ancient antenna, it is still being commonly used in modern handheld electronic devices.
There are already many studies on antenna improvement. One of which is a broadband antenna disclosed in TW Pat. No. 200924289. Nevertheless, such broadband antenna not only is structurally unstable that can fall over easily, but also is technically difficult to fabricate. Generally, an additional fixing element is required just for fixing such broadband antenna in an electronic device, and thus the production cost is increased.
There are another two antennas that are disclosed respectively in TW Pat. No. M260011 and M325616. In response to the broadband requirement of most modern electronic devices, the volumes of these two external antennas are comparatively larger so that they are not convenient in usage.